1. Field of the invention
This invention relates to the field of measurement systems utilized by the oil and gas industries.
2. The Prior Art
It is well known that logging tools and measurement-while-drilling (MWD) tools, which make measurements while traversing deep well boreholes, encounter large variations in borehole temperatures. In general, temperatures increase with depth, and very high temperatures are frequently encountered.
Many types of logging tools and several types of MWD tools contain scintillation detectors for measuring gamma radiation. Scintillation detectors incorporate a scintillator (crystal) for converting gamma rays or charged particles to light, photomultiplier tubes for converting the light to electronic signals, and electronics for processing the electronic signals. Although all of these detector components are subject to variation with temperature, the present state of the art of electronics is such that the electronics can be designed to be relatively insensitive to temperature within the desired operating range. However, the crystal and photomultiplier tubes are not insensitive to temperature variations; the result being large fluctuations in the detector response.